This proposal deals with certain aspects of the biochemistry and cell biology of eukaryotic messenger RNA. The particular mRNA chosen for study is ovalbumin mRNA, which codes for the major protein product of chicken oviduct. Ovalbumin is a secretory glycoprotein which is synthesized only in the continual presence of estrogen, either endogenously produced (laying hen) or exogenously administered (immature chick). Proteins which specifically associate with ovalbumin mRNA will be isolated and characterized in an attempt to further understand such processes as protection of mRNA from intracellular nucleases, segregation of different mRNAs between free and bound polyribosomes, and initiation of protein synthesis. The question of whether a precursor for ovalbumin mRNA exists will be investigated, making use of an affinity column. The covalent structure of the 5'-terminus of ovalbumin mRNA, presumed to be blocked and methylated by analogy to other mRNAs, will be determined. Finally, an hypothesis to account for the unusually long half-life of ovalbumin mRNA in vivo will be tested using estrogen-primed chicks.